1. Field of the Invention
The present invention relates to an air conditioner, and more particularly, to a multiple type air conditioner having a single outdoor unit and a plurality of indoor units.
2. Prior Art
In general, an air conditioner has an indoor unit installed in a room, and an outdoor unit installed outside the room. The indoor unit has an indoor heat exchanger to exchange heat with indoor air, and the outdoor unit has an outdoor heat exchanger to exchange heat with outdoor air.
A so-called multiple type air conditioner has been proposed, which operates a plurality of indoor units respectively installed in several places, using a single outdoor unit. Such a multiple type air conditioner, as shown in FIG. 3, has a single outdoor unit 52 and a plurality of indoor units 51. FIG. 3 shows a multiple type air conditioner having two indoor units 51, that is, a first and a second indoor units 51a and 51b.
The outdoor unit 52 has a compressor 53 to compress gaseous refrigerant to a high-temperature and high-pressure state, and an outdoor heat exchanger 54 to condense the refrigerant into a liquid refrigerant in a low-temperature and low-pressure state, by exchanging heat of the refrigerant compressed by the compressor 53 with outdoor air.
The first indoor unit 51a and the second indoor unit 51b respectively have a first indoor heat exchanger 55a and a second indoor heat exchanger 55b. The indoor heat exchangers 55 are connected with the compressor 53 by a first refrigerant pipe 58, the compressor 53 is connected with the outdoor heat exchanger 54 by the second refrigerant pipe 68, and the outdoor heat exchanger 54 is connected with the indoor heat exchangers 55 by a third refrigerant pipe 78. The first refrigerant pipe 58 is branched to a pair of branch pipes 75a and 75b, and the branch pipes 75a and 75b are connected to a pair of indoor heat exchangers 55a and 55b, respectively. The third refrigerant pipe 78 is also branched to a pair of branch pipes 65a and 65b, and the branch pipes 65a and 65b are connected to a pair of indoor heat exchangers 55a and 55b, respectively.
Valves 61a and 61b are respectively installed on the branch pipes 65a and 65b of the third refrigerant pipe 78. The valves 61a and 61b open and close the respective branch pipes 65a and 65b, and control the supply of refrigerant into the corresponding indoor heat exchangers 55a and 55b.
The first refrigerant pipe 58 and the second refrigerant pipe 68 intersect each other in one point, and a four-way valve 64 is installed on the intersecting point. According to operation of the four-way valve 64, the refrigerant compressed by the compressor 53 is supplied to the outdoor heat exchanger 54 or the indoor heat exchangers 55, selectively. Thus, the direction of the refrigerant is changed by the four-way valve 64, and thereby, the heating or cooling operations of the indoor air are performed selectively.
Meanwhile, such an air conditioner exchanges heat in the first and second indoor heat exchangers 55a and 55b, using the refrigerant compressed in a single compressor 53, so a compressor 53 having double the required capacity of compression in one indoor heat exchanger is employed. Thus, the compression capacity of the compressor 53 is surplus where either 55a or 55b of the indoor heat exchangers is being used, and therefore, a bypass pipe 70 is provided, in order to bypass the surplus compressed refrigerant.
The bypass pipe 70 connects a portion of the first refrigerant pipe 58 adjacent to the inlet of the compressor 53 to the outdoor heat exchanger 54 so that a part of the compressed refrigerant supplied from the compressor 53 into the outdoor heat exchanger 54 is directly circulated into the compressor 53. Furthermore, a bypass valve 71 is installed on the bypass pipe 70, which is generally comprised of a solenoid valve, and a capillary tube 72 for expanding the refrigerant bypassed toward the compressor 53 is disposed on the end portion of the bypass pipe 70.
While all of the indoor units 55 are operating, the bypass valve 71 closes the bypass pipe 70, and the valves 61 open the branch pipes 65. Then, the refrigerant compressed by the compressor 53 is circulated via the outdoor heat exchanger 54, the third refrigerant pipe 78, the branch pipes 65, the indoor heat exchangers 55, the branch pipes 75, the first refrigerant pipe 58, and the compressor 53, successively. In this course, the refrigerant is condensed in the outdoor heat exchanger 54 to thereby radiate heat, and the refrigerant evaporates in the indoor heat exchangers 55 to thereby absorb heat. Thus, the indoor air is cooled.
Meanwhile, while either of the indoor units 51a and 51b, for example the first indoor unit 51a, is operating, the bypass valve 71 opens the bypass pipe 70, the valve 61a opens the branch pipe 65a, and the valve 61b closes the branch pipe 65b. Then, the refrigerant compressed by the compressor 53 is circulated via the outdoor heat exchanger 54, the third refrigerant pipe 78, the branch pipe 65a, the first indoor heat exchanger 55a, the branch pipe 75a, the first refrigerant pipe 58, and the compressor 53, successively, and thereby, only the first indoor unit 51a performs the cooling operation. In this course, a part of the refrigerant flowing into the outdoor heat exchanger 54 is directly circulated into the compressor 53 via the bypass pipe 70 and the capillary tube 72.
However, in such a conventional multiple type air conditioner, the radius of and the length of the capillary tube 72 are predetermined when the outdoor unit 52 is manufactured, in consideration of the amount of the refrigerant to be expanded therein, so the amount of refrigerant flowing into the bypass pipe 70 cannot be adjusted in response to the change in length of the refrigerant pipe 78 for supplying the refrigerant into the indoor heat exchangers 55. In other words, temperature and pressure of the refrigerant which has passed through the indoor unit 51 vary from time to time according to operational states of the air conditioner; however, temperature and pressure of the refrigerant which has passed through the capillary tube 72 are constant. Therefore, when the refrigerant passing through the bypass pipe 70 meets the refrigerant circulated through the first indoor unit 55a in the first refrigerant pipe 58, noise is generated due to a difference in pressure between these refrigerants, and thereby, the operational efficiency of the compressor 53 is lowered.